Relationship between the C-13-NMR chemical shift and the carcinogenic activity of benz[a]anthracenes

A thorough NMR spectroscopic investigation was made on 7,12-dimethylbenz[a] anthracene (1) and the H-1- and C-13-NMR spectra were completely assigned, We compared the C-13-NMR chemical shifts (delta) of three benz[a]anthracenes, including compound 1, whose carcinogenicities vary largely, and investigated the relationship of the delta and carcinogenicity. It was found that the delta values at the Cl, C2, and C6 positions differed significantly between the carcinogenic and noncarcinogenic compounds.